(1) Field of the Invention
The present invention relates to programmer/timers. More specifically this invention relates to programmer/timers having a plurality of switches actuated in a timed sequence for controlling the operation of an appliance.
(2) Background Information
Appliance programmer/timers are commonly used in many household appliances, such as dishwashers, clothes washers, and clothes dryers. The appliance timer controls operation of the appliance by actuating and deactuating switch assemblies, which start and stop various work functions within the appliance, such as agitation, washing, spinning, drying, and others.
Cam-operated programmer/timers are complex electromechanical devices having many mechanical components, typically including a housing with a control shaft that serves as an axis of rotation for a drum-shaped cam, referred to as a camstack. The camstack is rotated via a drive system that is powered by an electric motor. When the camstack rotates, cam followers engage the cam blades and actuate and deactuate switch assemblies in response to the cam blade program. A knob is generally placed on the end of the control shaft, which extends through the appliance control consol for an operator to select an appliance program.
Recently, Joyce et al., in U.S. Pat. No. 5,637,843, hereinafter referred to as the ""843 patent, disclosed a programmer/timer with a cam disk. The ""843 patent is fully incorporated herein by reference. The cam disk has single working height cam tracks formed concentrically on one face thereof. A cam disk was employed to overcome undesired inaccuracies in making and breaking of side contact associated with timers employing a camstack construction, especially for those in which single pole double-throw (SPDT) type switching was required. The cam disk was also employed to provide a means of disengaging the cam from the followers to eliminate the noise associated with switch actuation and deactuation during setting of the program cam by a user.
While the programmer/timer disclosed in the ""843 patent represents a significant advancement, a programmer/timer with additional functionality and improved versatility is generally preferred in order to appropriately serve the numerous programmer/timer markets. Further improvements to simplify manufacturability and thereby reduce costs are also desirable.
One aspect of the present invention is an electromechanical programmer/timer for appliances of the type employing a rotatable cam disk that includes a plurality of cam tracks provided on an axial face of the disk. Upon advancement of the cam, the cam tracks effect sequential actuation and deactuation, through individual cam followers mounted on a plate assembly, of a plurality of appliance function control switches. The cam tracks in this invention include two or more working heights and the switches are configured for multiple working heights. The cam is retractably mounted such that it may be retracted axially from the plate assembly, permitting rotation of the cam without causing actuation of the switches. The programmer/timer of this invention employs a drive mechanism that advances the cam disk. In an optional variation, the drive mechanism may include a motor pinion that engages a perimeter gear on the cam disk. The programmer/timer of this invention may embrace numerous variations as described hereinbelow.